Embodiments of the present invention generally relate to characterizing cardiac function, and more particularly to methods and systems that analyze valve related timing and monitor heart failure.
Today, pacemaker configuration is often performed by selecting a desired lead location for a specific patient (e.g., apical vs septal) and then programming the parameters of the pacemaker, such as the AV and/or VV delay, the rate responsive AV and/or VV delay and the like. Today, cardiac resynchronization therapy (CRT) configuration is similarly performed by selecting a desired lead location (e.g., by avoiding infarct zones, reduced dyssynchrony, LV apical vs septal) and then programming the CRT device with desired AV and VV delays. The AV and VV delays are selected traditionally by physicians through the use of an echocardiography evaluation method. However, the echocardiography evaluation method is time consuming and has high variations.
In addition, device manufacturers have implemented algorithms within implanted medical devices that select AV and VV delays based on intra-cardiac electrograms (IEGM). For example, one device-based method uses P-wave duration to estimate intra-atrial conduction time (IACT) for setting the timing of ventricular (V) pacing. This device-based method is intended to achieve similar effects as an echocardiography evaluation based method. However, device-based methods that utilize the P-wave, as detected in the RA, represent a rough estimation of IACT. As such, the potential exists that the P-wave estimate may be an inaccurate estimate of IACT.
Device manufacturers have also implemented algorithm within implanted medical devices to detect heart failure (HF). HF is not a condition in which the heart abruptly stops beating. Instead, HF refers to a dysfunction in which the myocardial tissue fails to contract or relax properly.
Furthermore, it is preferred to tailor each device to the individual patient's underlying etiology and functional status. Yet, a comprehensive echocardiography evaluation assessment is time consuming and has high variations. Also, when the parameters of a pacemaker are set to a preferred setting, while a patient is in the clinic, the same parameter settings may not reflect the best parameter settings for the patient when the person is ambulatory and active. Thus a need exists for further improving AV delay algorithms.